For many years temperature control systems for homes and buildings have had provisions for setting back the temperature in the building for energy conservation and/or comfort during certain periods of time such as at night. Such systems have had various provision or control apparatus for restoring the temperature in the building after the setback time period. As the temperature conditioning load increases during the setback time period, the building temperature will drop much lower. The scheduling to bring the temperature back to normal, that is the pickup scheduling, will have to take into consideration that the lower the building temperature, the larger the pickup load is to restore the building temperature to the normal daytime temperature.
With the use of certain temperature conditioning apparatus, such as a refrigeration heat pump, a large pickup load requires auxiliary heating equipment such as electrical strip heat. In the interest of economy, the use of electrical strip heat may not be desirable. For that reason, as well as other reasons, such as the length of the pickup time, the possible equipment wear, capacity of the equipment, occupancy comfort, and efficiency, there became a need to limit the setback temperature under certain load conditions.
The present invention is concerned with a temperature control system having a building temperature conditioning load responsive apparatus for providing a signal to modify the amount of temperature deviation or setback and/or adjust the amount of setback throughout a selected setback time period in response to the building temperature conditioning load whereby, upon a pickup of the load to restore the temperature in a space back to normal, the pickup load is maintained within certain limits.